Many scientific, medical and industrial tasks involve the deployment of objects or instruments, which may need to be held aloft and manipulated in space for extended periods of time, resulting in repetitive stress to the user. The resulting repetitive stresses are known to be a cause of work-related trauma.
For example, work-related musculoskeletal disorders have been identified as a widespread problem amongst diagnostic medical sonographers and vascular technologists. In 2006, approximately 46,000 sonographer and vascular technologist job positions existed in the United States. A representative survey reported nearly 90% of sonographers and vascular technologists report completing ultrasound scans while in some form of pain. Aggravating factors for pain during procedures was reported by sonographers to include sustained and repeated twisting of the neck and body, sustained arm abduction and application of pressure on the ultrasound transducer.
In a further example, heavy tools or parts may require maneuvering in repetitive or awkward motions by workers within industrial settings. Workers may also be required to maintain fixed poses for extended periods of time. Poor ergonomics adversely affect the productivity as well as the health and safety of workers within industrial settings.
To improve worker ergonomics, various devices have been developed to counterbalance objects and instruments, including, but not limited to, heavy tools or parts. While fixed arm supports and supports that permit some lateral motion are known in the art, some tasks require a larger range of horizontal and vertical motions, preferably at least two or three degrees of freedom (“DOF”). Industrial, medical and scientific operations, including, but not limited to surgical, industrial, diagnostic and therapeutic procedures, could greatly benefit from having gravity effectively negated for the user in a manner that can provide larger ranges of motion in an isoelastic manner. The term isoelastic may refer to the application of a constant force by a user to move the arm throughout its full range of motion. For example, Equipois Inc. (Manchester, N.H.) have developed spring loaded counterbalancing arms (e.g., the zeroG™ mechanical arm) including self-supporting counterbalancing arms adapted to position tools and parts in industrial settings employing serially connected parallelogram segments. Springs may be used to counterbalance the load and any subsequent segments in the arm. The preload of the spring in each segment may be adjusted to accommodate loads of varying weights.
Such prior art devices may present drawbacks however. To adjust the load carrying capacity of the arm, the user may be required to make multiple adjustments to various elements making the use thereof slow and cumbersome. If the arm is not isoelastic, the user may experience inconsistent performance as the user may need to use greater force to adjust the arm in different positions. The isoelasticity of the zeroG™ may be inversely related to the amount of rate adjustment. As rate adjustment increases to allow operation at extreme angles, isoelasticity may decrease degrading overall performance throughout the full range of motion.
In the field of diagnostic medical sonography and vascular technology, for example, previous counterbalancing arms may have used high torque motors to counterbalance the load weight creating potential harm for a patient. In the event of a malfunction, the motors may potentially drive the arm into the patient with a minimum force of twice the weight of the arm. In the event of a power failure, a traditional arm may lose its pose and slump under its own weight as the motors can no longer counterbalance the weight. While brakes may have been applied to prevent traditional arms from slumping in a power failure, the traditional arm may become fully locked (i.e., un-adjustable) until power is restored.
What is needed is a counterbalance apparatus and/or method that overcomes one or more of the limitations associated with the prior art. It may be advantageous to provide an apparatus and/or method which facilitate the counterbalancing of loads having different weights.
Prior attempts, if any, to solve problems associated with prior art devices and/or methods may have been unsuccessful and/or had one or more disadvantages associated with them. Prior art devices and/or methods have been ill-suited to solve the stated problems and/or the shortcomings which have been associated with them.
It is an object of the present invention to obviate or mitigate one or more of the aforementioned disadvantages and/or shortcomings associated with the prior art, to provide one of the aforementioned needs or advantages, and/or to achieve one or more of the aforementioned objectives of the invention.